Group III-V compound semiconductor materials such as GaN, AlGaN, and the like have various advantages such as wide, easily adjustable energy band gaps, and thus have been widely used for electronic devices in the field of optoelectronics.
Particularly, light emitting devices using Group III-V or II-VI compound semiconductor materials, such as light emitting diodes or laser diodes, have advantages in that they may be used to realize various colors such as red, green, blue, and ultraviolet (UV) colors with the development of thin film growth technology and device materials, and may also be used to realize highly effective white light beams by making use of fluorescent materials or combining colors, and have low power consumption, semi-permanent lifespan, rapid response time, safety, and environmental friendliness, compared to conventional light sources such as fluorescent lamps, incandescent lamps, etc.
Therefore, the light emitting devices have been increasingly applied to transmitter modules for optical communication systems, light emitting diode backlight units replacing cold cathode fluorescence lamps (CCFLs) constituting backlight units for liquid crystal display (LCD) devices, white light emitting diode lightings capable of replacing fluorescent lamps or incandescent lamps, car headlights, and traffic lights.
FIG. 1 is a diagram showing a conventional light emitting device.
A light emitting device 100 includes a substrate 110 formed of sapphire, and the like, a light emitting structure 120 arranged on the substrate 110 and including a first conductive semiconductor layer 122, an active layer 124, and a second conductive semiconductor layer 126, and a first electrode 160 and a second electrode 170 arranged on the first conductive semiconductor layer 122 and second conductive semiconductor layer 126, respectively.
As electrons injected through the first conductive semiconductor layer 122 and holes injected through the second conductive semiconductor layer 126 are combined at the active layer 124, the light emitting device 100 emits light with energy determined by an innate energy band of a material used to form the active layer 124. The light emitted from the active layer 124 may have varying colors, depending on compositions of the material forming the active layer 124. In this case, the light may include blue light, UV or deep UV rays, etc.
The light emitting device 100 may be arranged in a light emitting device package. In this case, light with a first wavelength region emitted from the light emitting device 100 may excite a phosphor, which then may emit light with a second wavelength region as the phosphor is excited by the light with the first wavelength region. Here, the phosphor may be included in a molding part surrounding the light emitting device 100, or may be arranged in the form of a phosphor film.
However, the above-described conventional light emitting device has the following drawbacks.
In the light emitted from the active layer 124, light traveling toward the second electrode 170 may be absorbed into the second electrode 170, resulting in degraded light efficiency of the light emitting device 100.